The present invention relates to the field of optical communications. In recent years, increasing interest and attention have been attracted to processing and transmitting large amounts of communications information from many sources to many destinations on tiny beams of light carried in optical waveguides. In order to route information from each source to each destination, it is necessary to provide modulating apparatus for first impressing the information upon light at its source. Then the light is switched appropriately along its way so that it follows a path to its intended destination at the same time as other sources of light are switched or coupled along correct paths to their correct destinations.
In the prior art a variety of modulator and switch devices have been proposed which use substrates of crystalline material such as gallium arsenide (GaAs), lithium niobate (LiNbO.sub.3), or lithium tantalate (LiTaO.sub.3), the optical properties of which are sensitive to electric fields produced by means of a voltage source connected to electrodes deposited thereon. The amount of light leaving such a device can be varied in its intensity or amplitude for modulation or can be turned on and off in intensity in a given direction when switching action is desired.
The suitability of a given modulator or switch device relates to practical considerations.